Support band for movable flexible cable assembly

ABSTRACT

The present invention provides a flexible cable and support band assembly which is dynamically stable at high speeds over long lengths. This has been accomplished by cupping both the flexible cable and the support band in cross section along their lengths so that they cup one within the other to essentially move as a unit even though they are not attached except at their ends. A single support band can be employed to support multiple flexible cables. Additional support has been provided by employing resilient spaced apart strips along a track upon which the one or more flexible cables and support band slide. The resilient strips center the travel of the one or more flexible cables and support band and minimize rocking motion and vibration. Still further the one or more flexible cables and support band are arranged with respect to a robotic media library so that a single length of the one or more flexible cables and the support band will serve a range of lengths of the library.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 08/338,292filed Nov. 14, 1994, now U.S. Pat. No. 5,669,749.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a movable flexible cable and supportband assembly and more particularly to a support band which supports oneor more flexible cables, the band and cable looping back on themselvesand moving with a movable component, such as an accessor in a roboticmedia library.

2. Description of the Related Art

Automated data storage libraries which archive magnetic tape andmagnetic or optical disks have become important for storing largeamounts of data. A typical magnetic tape library has a wall ofreceptacles or bins which store numerous magnetic tape cartridges, andincludes one or more tape drives. Such a library typically includes anaccessor that moves horizontally and carries a vertically positionablecartridge picker for transporting cartridges between receptacles and adrive. It is desirable that such a library be modular so that it can befashioned to meet the capacity of a user and can be easily changed insize if the user's requirements change.

An accessor executes cycles of fast movement. A host system transmitspower and control signals to the accessor via a flexible cable which isconnected to the accessor and which moves therewith. The flexible cablefolds back on itself in a loop so that it can be easily extended fromone end of the library to the other. The loop is continually subjectedto extreme stress yet it must be capable of functioning reliably formillions of cycles without failure. During this time the cable must beprevented from sliding upon itself in order to prevent wear and galling.Wear can render the cable inoperative and galling produces debris whichcontaminants the library.

A solution to the debris problem is addressed in commonly assigned U.S.Pat. No. 5,343,989 which describes stainless steel tabs mounted onflexible cable to prevent galling. Another solution is to loop theflexible cable around a pulley or spool which is attached to a spring.The spring keeps the flexible cable taut to prevent rubbing. A furtherscheme is to drape the flexible cable over spaced apart moving rollers.Still another scheme is to enclose the flexible cable in an articulatedmoving cage which provides gravity support. Some of these schemes areunduly complex, costly and must be designed and used with care toprevent damage to the cable.

In U.S. Pat. No. 4,898,351 a flexible cable is supported by a supportband over relatively short lengths in a printer or a typewriter. Theflexible cable and the support band are coextensive in length and movetogether back and forth about a loop as described hereinabove. Thesupport cable is cupped in cross section so that it has increasedlengthwise strength in the same manner as a steel measuring tape. Theflexible cable is flat and essentially makes line contact with thesupport band along its length. For short lengths this scheme providesadequate stability. This scheme is not satisfactory for long lengths asfound in a tape library. The line contact between the flexible cable andthe support band causes the flexible cable to be unstable. Thisinstability allows rocking motion at high speeds which causes stress andshortens the life of the flexible cable.

SUMMARY OF THE INVENTION

The present invention provides a movable flexible cable and support bandassembly which is dynamically stable at high speeds over long lengths.This is accomplished by providing the flexible cable with a cupped crosssection which matches or is concentric with the cupped cross section ofthe support band. With this arrangement, one cupped element is cuppedwithin another cupped element so that the flexible cable and the supportband cooperate in a unitary fashion as they move together even thoughthey are unattached except at their ends. The inventors have found thatthis scheme provides stability even though multiple flexible cables aresupported by a single support band. By employing multiple flexiblecables the power and signal requirements of large tape libraries can bemet.

The inventors have also discovered that stability of the one or moreflexible cables and the support band is even further increased byproviding resilient guides along an elongated support plate upon which abottom length of the combined flexible cable and support band slide. Ina preferred embodiment a pair of spaced apart rubber-like strips extendalong the plate to guide the one or more flexible cables and supportband. This guidance centers travel along the support plate, preventsrocking motion and dampens vibrations of the one or more flexible cablesand support band as they move rapidly to various locations in thelibrary.

The inventors have further discovered that by proper placement a singlelength of one or more flexible cables and support band will serve arange of sizes of a library arranged in modular form. For instance onelength is provided which will serve a one or two frame library, a longerlength is provided which will serve a three or four frame library and astill longer length is provided which will serve a five to eight framelibrary.

An object of the present invention is to provide a flexible cable andsupport band assembly which is stable when moved at high speeds overlong lengths.

Another object is to provide a combined flexible cable and support bandwhich can move at high speeds in a straight line along a track withminimum rocking motion and vibration.

A further object is to provide a flexible cable and support band schemewhich will serve a range of sizes of library lengths.

Still another object is to provide a robotic media library which has asimplified arrangement for delivering power and signals between a hostand an accessor.

Still a further object is to provide a robotic media library which has adynamically stable flexible cable and support band assembly which willserve a range of library lengths.

These and other objects will become more apparent to one skilled in theart upon reading the following specification with reference to theaccompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of the present invention.

FIG. 2 is a top plan view of FIG. 1.

FIG. 3 is a cross section through a prior art flexible cable and supportband assembly.

FIG. 4 is view taken along plane IV--IV of FIG. 1.

FIG. 5 is an enlarged isometric view of a U shaped guide rail, shown incross section in FIG. 4, with a portion of the rail cut away to show thepair of resilient strips.

FIG. 6 is an isometric view of an exemplary magnetic tape library whichshows the flexible cable and support band assembly of the presentinvention.

FIG. 7 is a side view of a flexible cable and support band making a loopand having a connector at each end.

FIG. 8 is a plan view of the support band and connectors before beinglooped.

FIG. 9 is a view taken along plane IX--IX of FIG. 8 with the connectorsexploded.

FIG. 10 is a view taken along plane X--X of FIG. 8.

FIG. 11 shows cross sections of top and bottom lengths of a pair offlexible cables and single support band after they are looped, thethicknesses of the cable and band being greatly exaggerated to showthickness relationships.

FIG. 12 is a chart of stress in steel bands versus band thicknesses forvarious loop radii and various cup radii.

FIG. 13 is a chart of percentage of ultimate tensile stress in steelbands versus band thickness for various loop radii and various cupradii.

FIGS. 14A-14E illustrate a prior art arrangement of a flexible cable andsupport band assembly for a modular media library.

FIGS. 15A-15E illustrate an arrangement of a flexible cable and supportband assembly for a modular media library according to the presentinvention.

FIGS. 16A-16D, FIGS. 17A-17B and FIGS. 18A-18B illustrate how the schemeillustrated in FIGS. 15A-15E enables a single length of flexible cableand support band to serve various library lengths.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views, there is illustratedin FIG. 1, a movable flexible support band assembly 20 which may beemployed to provide power and control signals for a robotic magnetictape cartridge library which will be described in more detailhereinafter. The assembly includes an elongated support, such as a Ushaped channel 22. Resting within the channel is a flexible cable 24 anda support band 26, the flexible cable having first and second ends 28and 30 and the support band having first and second ends 32 and 34. Theflexible cable 24 and the support band 26 are curved along their lengthsto form a loop at 36 and 38, respectively, with first and second lengthsof each of the flexible cable and support band extending therefrom. Theflexible cable and the support band are co-extensive and substantiallyengage one another along their lengths.

The first end 28 of the flexible cable is fixed to or fixed inrelationship to the channel 22 and is connected to power supply andcontrols 40. The first end of the support band 32 may be commonly fixedin relationship to the channel 22 which will be described in more detailhereinafter. The second end 30 of the flexible cable and the second end34 of the support band may be connected to an accessor 42 whichreciprocates horizontally back and forth within a tape library. Theaccessor makes many starts and stops and moves at high speeds whichsubjects the flexible cable to highly dynamic rocking and vibrationalforces. FIG. 2 is a top view of FIG. 1.

FIG. 3 illustrates a prior art flexible cable and support band assemblywhich employs a flat flexible cable 46 in engagement with a cuppedshaped support band 48. Because the support band 48 is cupped incross-section it provides support for the flexible cable in the samemanner as a self-supporting steel measuring tape. The assembly 44 hasbeen employed for printing devices and typewriters which operate atshort lengths. In long lengths, such as a magnetic tape library, theflexible cable operates under much higher dynamic loading. Morespecifically, the longer lengths subjects the flexible cable tovibration and torsional forces due to rocking motion. The line contact50 made between the flexible cable and the support band in the prior artassembly, leaves a majority of width of the flexible cable unsupportedcausing it to rock and vibrate.

We have discovered that by providing each of the flexible cable 24 andthe support band 26, with a cross section as illustrated in FIG. 4, thatthe flexible band completely supports the flexible cable across itswidth over long lengths so as to minimize rocking motion and vibrationof flexible cable as it rapidly reciprocates back and forth in a tapelibrary. In a preferred embodiment, the flexible cable and the supportband are cupped upwardly along their bottom lengths with the flexiblecable below the support band and the flexible cable and support band arecupped downwardly along their upper lengths with the flexible cable ontop of the support band and being supported by the support band betweenthe loop 38 and the second end 30 of the flexible cable. In someembodiments it may be desirable to cup the flexible cable 24 and thesupport band 26 downwardly along their bottom lengths and cup theflexible cable and the support upwardly along their upper lengths.Further, the assembly 20 may be oriented vertically, instead ofhorizontally, in which case it is preferred that the support band belocated inwardly of the flexible cable within the loop. In allembodiments, however, one of the flexible cable and the rigid band arecupped within the other of the flexible cable and the rigid band. Thisunique relationship allows the support band to support more than oneflexible cable which will be described in more detail hereinafter.

We have discovered additional means for minimizing rocking motion andvibration of the flexible cable during high speed travel. As shown inFIGS. 4 and 5, this has been accomplished by providing resilient strips52 and 54 which are fixed in a spaced relationship in a bottom plate 56of the channel 22. The resilient strips are spaced one on each side ofthe center of the width of each of the flexible cable 24 and the supportband 26 so that the flexible cable and the support band have limitedrocking movement as they travel above the plate 56. The strips 52 and 54provide guidance for the flexible cable and the support band. The stripscenter the travel of the flexible cable and the rigid band along theplate 56 and dampen vibration forces. In some embodiments, discrete padsmay be used in lieu of strips. It is desirable that the strips beconstructed of a foam rubber like material. The material of the stripscan be rubber, neoprene or plastic. While the strips are shown asrectangular in cross-section, they could be curved to match the cuppingof the flexible cable and support band.

FIG. 6 illustrates an exemplary magnetic tape cartridge library 60 whichmay employ the flexible cable 24 and support band 26 assembly of thepresent invention. This library has multiple frames 62, each frame beingseparable and having a plurality of receptacles or bins for storing aplurality of tape cartridges (not shown) and drives (not shown).Accordingly, the library can be sized to meet the capacity requirementsof a user. The accessor carries a cartridge picker 64, which is movablevertically on a movable support 66 so that with combined horizontal andvertical movements the picker 64 can pick a tape cartridge from any binwithin the library. It should be understood that this type of librarycan be employed for magnetic tape cartridges or magnetic or opticaldisks. The second ends of the flexible cable and support band areconnected at a center location 68 of the library, which support themodular concept of the library to be described in more detailhereinafter. As the accessor 64 moves from frame 8 to frame 1, the loopmoves from near the center location 68 to frame 1.

We have provided a unique connector for connecting each end of theflexible cable and support cable, as shown in FIGS. 7-10. As shown inFIG. 10, the connector 70 includes a pair of plates 72 and 74, which arecupped to clamp of the flexible cable and the support band. End portionsof the flexible cable and the support band are located between theplates and are squeezed therebetween and tightly secured when the platesare affixed together by bolts 76. The end portion of the support band 26may be extended by a thin welded plate 77 of a larger width so that thebolts 76 do not penetrate and weaken the end of the support band. One ofthe connectors may be rigidly fixed to the accessor and the otherconnector 70 may be rigidly fixed to the U shaped channel. Theembodiment shown in FIG. 10 illustrates the assembly as including onesupport band and two flexible cables, which will be described in moredetail hereinafter. As shown in FIGS. 8 and 9, the right connector maybe connected at the center location within the library, which is shownat 68 in FIG. 6. The left connector, which is connected to the accessor42, makes a loop to the right and above the right connector and theflexible cables 24 may extend from the right connector to a terminal endof the library for connection to power supplies and controls 40, whichis shown in FIG. 1. A plug 78 may connect the one or more flexiblecables to the accessor 42 and a plug 79 may connect the one or moreflexible cables to power supply and control 40.

FIG. 11 is an illustration of an exaggerated thickness of the supportband 24 and a pair of flexible cables 26. Each flexible cable includes aplurality of conductors 80 which are embedded in a flexible material,such as a polymer. The preferred material for the support band 24 isstainless steel AISI 302. We have found that an acceptable ratio ofthicknesses of each of the flexible cables to the support band is 3to 1. We have constructed an embodiment of the invention wherein thethickness "a" of the support band is 0.010 inches and the thickness "b"of each of the flexible cables is substantially 0.011 inches. The widthof each of the support band and the flexible cable is substantially 65millimeters. The loop of each of the flexible cables and the supportband has a radius of substantially 60 millimeters and the cupping ofeach of the support band and the flexible cable is an arc with a radiusof substantially 78 millimeters. The less the radius of the arc thegreater the support provided by the support band 24. However, this hasto be balanced with respect to the stress placed on the support band dueto the cupping as well as the stress placed on the support band at itsloop. The cupping radius has a major effect on the loop diameter, asdiscussed by K. Schulgasser in an article entitled; "Configuration of aBent Tape of Curved Cross Section", in Journal of Applied Mechanics ofthe ASME, "JNL APPL MECH TRANS ASME", Vol. 59 N3 September 1992, page692-693. FIGS. 12 and 13 show the stress in the support bands and thestress in the support bands as a percentage of ultimate tensile strengthversus various thicknesses of the bands for various cup radii and loopradii. As can be seen from FIG. 13, exceeding the ultimate tensilestrength of stainless steel is an important factor to consider. We havefound that by employing a support band with a thickness of 0.010 inchesthat the ultimate tensile strength can be kept to about the 35 level,with a loop radius of about 60 millimeters.

Referring now to FIGS. 14A-14E, there is illustrated a prior artconnection of the flexible cable and support band assembly. In FIGS.14A-14E, the first ends of the flexible cable and the support band areconnected at a terminal end 82 of the library in contrast to the centrallocation 68, located in FIG. 6. It can be seen from FIGS. 14A-14E thatthe assembly can only serve one size of library. As example, if aparticular length of the assembly serves eight frames within thelibrary, as illustrated in FIGS. 14A-14E, the assembly cannot serve alesser number without the loop of the assembly extending beyond the endof the library. We have found by connecting one or more of the flexiblecables and the support band at the central location 68, as illustratedin FIGS. 15A-15E, that the assembly can serve a range of sizes oflibraries. The range of sizes of libraries that the assembly in FIGS.15A-15E can serve is illustrated in FIGS. 16A-16D. This range is from5-8 frames. With the first ends of the flexible cable and the supportconnected at 68, the accessor can serve 5 frames, 6 frames, 7 frames or8 frames, as shown in FIGS. 16A-16D, respectively. With a shorter lengthof the assembly connected at 68, the assembly can serve 3 or 4 frames,as shown in FIGS. 15A and 15B, respectively. With still shorter lengthof the assembly connected at 68, the accessor can serve 1 or 2 frames,as illustrated in FIGS. 17A and 17B.

We have now described a unique arrangement for optimizing dynamicstability of one or more flexible cables and support band assembly. Bycupping the cross-section of both the support band and one or moreflexible cables, the one is cupped within the other, with their arcssubstantially in a concentric relationship. Accordingly, the supportband and the one or more flexible cables move virtually as a unitaryelement along their first and second lengths and the loops therebetween.Because of the stability, more that one flexible cable can be supportedby the support band which is a preferred embodiment. Further dynamicstability is provided by the assembly by providing the longitudinallyresilient strips along a support plate, along the bottom of the bottomlength of the assembly. These strips center the movement of the flexiblecables and support band along a track, restrict rocking movement of theassembly and dampen vibrations. A unique connector has been provided forcommonly connecting first end portions and/or second end portions of theflexible cables and support band. The invention further teachesconnecting the first ends of the flexible cables and the support band ata center location in the largest library of a range of sizes oflibraries so that the assembly can serve the range of sizes.

Obviously many modifications and variations of the invention arepossible in light of the above teachings. Therefore, the invention maybe practiced otherwise than as specifically described as stated in thefollowing claims.

We claim:
 1. A movable flexible cable support band assemblycomprising:an elongated support; at least one flexible electrical cablehaving a fixed end, which is fixed at a predetermined location on saidelongated support, and a free end which is free to move with respect tosaid predetermined location; an elongated support band having a fixedend, which is fixed at said predetermined location, and a second endwhich is free to move with respect to said predetermined location; saidfree ends being interconnected; each of the flexible electrical cableand the support band having a cross section which is cupped along itsrespective length with one of the flexible electrical cable and thesupport band being cupped within and engaging the other one of theflexible electrical cable and the support band along their lengths; theflexible electrical cable and the support band being curved along theirlengths to form a loop between said first and second ends and havingfirst and second elongated extensions that extend from the loop parallelto a longitudinal axis of the support to said first and second endsrespectively; motive power means connected to the free ends andelectrically connected to said at least one flexible electrical cablefor moving the free ends parallel to said longitudinal axis; and roboticmeans connected to the motive power means and electrically connected tosaid at least one flexible electrical cable for accessing articles. 2.An assembly as claimed in claim 1 including:the cup shape of each of theflexible electrical cable and the support band being an arc; and the arcof each of the flexible electrical cable and the support band beingconcentric along their lengths.
 3. An assembly as claimed in claim 1wherein said at least one flexible electrical cable is a plurality offlexible electrical cables.
 4. An assembly as claimed in claim 1including:the fixed ends of the flexible electrical cable and thesupport band being fixedly connected by a connector; and said connectorcomprising:a pair of plates which are cupped to clamp the flexibleelectrical cable and the support band; end length portions of theflexible electrical cable and the support band being located betweensaid plates; and means securing the plates together so that the platessqueeze the end length portions of the flexible electrical cable and thesupport band therebetween in a fixed relationship.
 5. An assembly asclaimed in claim 1 wherein the elongated support includes a U-shapedchannel supporting the first elongated extensions of the flexibleelectrical cable and the support band.
 6. An assembly as claimed inclaim 1 including:the support band being steel; and the flexibleelectrical cable being a plurality of conductors embedded in a polymer.7. An assembly as claimed in claim 1 including:the elongated supportincluding a channel for supporting said first elongated extensions; andresilient means mounted to the channel for guiding movement of theflexible electrical cable and the support band.
 8. An assembly asclaimed in claim 7 including:the resilient means comprise a pair ofstrips which are fixed to the channel in a spaced apart lateralrelationship which is less than a width of the flexible electrical cableor the support band.
 9. An assembly as claimed in claim 7 wherein saidat least one flexible electrical cable is a plurality of flexibleelectrical cables.
 10. An assembly as claimed in claim 7 including:thechannel and the first and second extensions of the flexible electricalcable and the support band being oriented in horizontal directions withthe first extensions of the flexible electrical cable and the supportband being at a bottom location adjacent the channel and the secondextensions of the flexible electrical cable and the support band beingat a top location above said bottom location.
 11. An assembly as claimedin claim 10 including:the flexible electrical cable being below thesupport band along said first extension and being above the support bandalong said second extension.
 12. An assembly as claimed in claim 11wherein the resilient means includes a pair of strips which are fixed tothe channel in a spaced apart lateral relationship which is less than awidth of the flexible electrical cable or the support band.
 13. Anassembly as claimed in claim 12 wherein said at least one flexibleelectrical cable is a plurality of flexible electrical cables.
 14. Anassembly as claimed in claim 13 wherein the elongated strips are foamrubber, neoprene or silicone.
 15. An assembly as claimed in claim 1including:the robotic means being capable of accessing a plurality ofreceptacles in a plane parallel to said first and second extensions; andsaid predetermined end being located intermediate a length of thesupport.
 16. An assembly as claimed in claim 15 including:each of thefixed ends of the flexible electrical cable and the support band beingfixedly connected to the support by a respective connector; and saidconnector comprising:a pair of plates which are cupped to match thecupping of the flexible electrical cable and the support band; endlength portions of the flexible electrical cable and the support bandbeing located between said plates; and means securing the platestogether so that the plates squeeze the end length portions of theflexible electrical cable and the support band therebetween in a fixedrelationship.
 17. An assembly as claimed in claim 15 including:the cupshape of each of the flexible electrical cable and the support bandbeing an arc; and the arcs of the flexible electrical cable and thesupport band being concentric.
 18. An assembly as claimed in claim 15wherein said at least one flexible electrical cable is a plurality offlexible electrical cables.
 19. An assembly as claimed in claim 15including:the channel and the first and second extensions of theflexible electrical cable and the support band being oriented inhorizontal directions with the first extensions of the flexibleelectrical cable and the support band being at a bottom locationadjacent the channel and the second extensions of the flexibleelectrical cable and the support band being at a top location above saidbottom location.
 20. An assembly as claimed in claim 19 wherein said atleast one flexible electrical cable is a plurality of flexibleelectrical cables.
 21. An assembly as claimed in claim 20 including:thecup shape of each of the flexible electrical cable and the support bandbeing an arc; and the arcs of the flexible electrical cable and thesupport band being concentric.
 22. An assembly as claimed in claim 21including:the fixed ends of the flexible electrical cable and thesupport band being fixedly connected to the elongated support by aconnector; and said connector comprising:a pair of plates which arecupped to clamp the flexible electrical cable and the support band; endlength portions of the flexible electrical cable and the support bandbeing located between said plates; and means securing the platestogether so that the plates squeeze the end length portions of theflexible electrical cable and the support band therebetween in a fixedrelationship.
 23. An assembly as claimed in claim 1 including:the motivepower means including an elongated channel for supporting said firstelongated extensions; and the channel and the first and secondextensions of the flexible electrical cable and the support band beingoriented in horizontal directions with the first extensions of theflexible electrical cable and the support band being at a bottomlocation adjacent the channel and the second extensions of the flexibleelectrical cable and the support band being at a top location above saidbottom location.
 24. An assembly as claimed in claim 23 including:thecup shape of each of the flexible electrical cable and the support bandbeing an arc; and the arcs of the flexible electrical cable and thesupport band being concentric.
 25. An assembly as claimed in claim 24including:resilient means mounted to the channel for guiding movement ofthe flexible electrical cable and the support band.
 26. An assembly asclaimed in claim 25 wherein the resilient means includes a pair ofstrips which are fixed to the channel in a spaced apart lateralrelationship which is less than a width of the flexible electrical cableor the support band.
 27. An assembly as claimed in claim 26including:the robotic means being capable of accessing a plurality ofreceptacles in a plane parallel to said first and second extensions; andsaid predetermined end being located intermediate a length of thesupport.
 28. An assembly as claimed in claim 27 wherein said at leastone flexible electrical cable is a plurality of flexible electricalcables.
 29. An assembly as claimed in claim 28 including:the supportband being steel; and the flexible electrical cable being a plurality ofconductors embedded in polyethylene.
 30. An assembly as claimed in claim29 including:the fixed ends of the flexible electrical cable and thesupport band being fixedly connected to the support by a connector; andsaid connector comprising:a pair of plates which are cupped to match thecupping of the flexible electrical cable and the support band; endlength portions of the flexible electrical cable and the support bandbeing located between said plates; and means securing the platestogether so that the plates squeeze the end length portions of theflexible electrical cable and the support band therebetween in a fixedrelationship.
 31. An assembly as claimed in claim 30 wherein theelongated support includes a U shaped channel.
 32. An assembly asclaimed in claim 31 including:the plurality of flexible electricalcables being two; and a thickness of the support band beingsubstantially one third a thickness of a flexible electrical cable. 33.An assembly as claimed in claim 32 wherein the elongated strips are foamrubber, neoprene or silicone.